Spin flow necking is a process of necking-in an open end of a metal container to provide a flange which allows a can end to be seamed thereto after filling. Necking also makes conveying of the cans easier since, with only slight flange overlap, the cans contact body-to-body instead of flange-to-flange which would otherwise cause tilting and conveying jams.
While numerous necking processes have been developed since the 1970's, a particularly promising spin flow process and apparatus having the potential of allowing can ends to be necked-in to increasingly smaller diameters is disclosed in U.S. Pat. No. 4,781,047, issued Nov. 1, 1988 to Bressan, which is assigned to Ball Corporation and is exclusively licensed to the assignee of the present invention, Reynolds Metals Company. The disclosure of this patent is hereby incorporated by reference herein in its entirety. It concerns a process where an externally located free spinning form roll 11 (FIG. 1) is moved inward and axially against the outside wall C' of the open end C" of a rotating trimmed can C to form a conical neck at the open end thereof- With reference to FIG. 1, a spring-loaded holder or slide roll 19 supports the interior wall of the can C and moves axially under the forming force of the free roll 11. This is a single operation where the can rotates and the free roll 11 rotates so that a smooth conical necked end is produced. In practice, the can is then flanged. The term "spin flow necking" is used in this application to refer to such processes and apparatus, the essential difference between spin flow necking and other types of spin necking being the axial movement of both the external roll 11 and the internal support 19.
More specifically, the spin flow tooling assembly 10 depicted in FIG. 1 (corresponding to FIG. 1 of the Bressan et al '047 patent, supra) includes a necking spindle shaft 16a rotatable about its axis of the rotation A by means of a spindle gear 16 mounted to the shaft between front and rear bearings (not shown). The slide roll 19 is mounted to the front end of the necking spindle shaft 16a through a slide mechanism 28, keyed to the shaft, which permits co-rotation of the roll 19 while allowing it to be slid by the necking forces described more fully below in the axially rearward direction B' away from the eccentric freewheeling roll 24 located adjacent the front face of the slide roll. The axially fixed idler roll 24, having an axis of rotation B which is parallel to and rotatable about spindle axis A, is mounted via bearings 16b and 23 to an eccentrically formed front end of an eccentric roll support shaft 18. This shaft 18 extends through the necking spindle shaft 16a. The spindle shaft 16a is rotated by the spindle gear 16 without rotating the eccentric roll support shaft 18.
The outer form roll 11 is mounted radially outwardly adjacent the slide and eccentric rolls 19,24.
The container slide roll 19 is shaped with a conical leading edge 19a designed to first engage the open end C" of the container C to support same for rotation about spindle axis A under the driving action of the necking spindle gear 16 which may be driven by the same drive mechanism driving each base pad assembly 29 engaging the container bottom wall. Slide roll 19 is also free to slide axially but is resiliently biased into the container open end C" via springs 20 which may be of the compression type.
In operation, the container open end C" engages and is rotated by the slide roll 19. The eccentric roll 24 is then rotated into engagement with a part of the inside surface of the container side wall C' located inwardly adjacent the open end C". With reference to FIGS. 2A-2E, the external form roll 11 then begins to move radially inward into contact with the container side wall C' spanning the gap respectively formed between the conical faces 19a,24e of the slide and eccentric rolls 19,24. More specifically, the side wall C' of the spinning container body C is initially a straight cylindrical section of generally uniform diameter and thickness which may extend from a pre-neck (not shown) previously formed in the container side wall such as by static die necking. As the external form roll 11 engages the container side wall C', it commences to penetrate the gap between the fixed internal eccentric roll 24 and the axially movable slide roll 19, forming a truncated cone (FIG. 2B). The side wall of the cone increases in length as does the height of the cone as the external form roll chamfer 11c continues to squeeze or press the container metal along the complemental slope or truncated cone 24e of the eccentric roll 24 as depicted in FIG. 2C. The cone continues to be generated as the external form roll 11 advances radially inwardly (the slide roll 19 continues to retract axially as a result of direct pushing contact from roll 11 through the metal) until a reduced diameter 124 is achieved as depicted in FIGS. 2C and 2D. As the cone is being formed, the necked-in portion 124 or throat of the container C conforms to the shape of the form portion of the forming roll 11. The rim portions 123 of the neck which extend radially outwardly from the necked-in portion 124 are being formed by the complemental tapers 11b,19a of the form roll 11 and the slide roll 19 to complete the necked-in portion.
The above-described spin flow necking process, while producing a large diameter reduction in the open end of the container C (e.g., 0.350"), has various drawbacks when applied to two-piece aluminum can manufacture. One drawback, for example, is grooving of the neck at the initial point of contact between rolls 11,19 in FIG. 2B which occurs on the inside of the container as a result of the small radii on the form roll pushing past and against the small radii on the slide roll as the form roll moves radially inwardly and axially rearwardly during the necking process along the chamfer 24e of the eccentric roll. Due to the force of spring 20 urging the slide roll 19 toward the eccentric roll 24, the metal caught between these colliding radii (which are forcefully pressed together under spring bias) is grooved on both the inner and outer surfaces of the neck. On the inside surface, this grooving results in metal exposure (i.e., wearing away of the protective coating) which often allows the beverage to "eat through" the container side wall C'. It has also been discovered that such grooving often results in actual cutting of the metal as the form roll 11 is radially inwardly advanced from the position depicted in FIG. 2B to that of FIG. 2C.
As the form roll 11 moves into its radially inwardmost position depicted in FIG. 2E, the spring pressure acting against the slide roll 19 in the direction of the form roll disadvantageously results in pinching of the end of the flange-like portion 123 and undesirable thinning of the metal. In some cases, particularly when necking a can to smaller diameters (e.g., 204 or 202), the edge is sometimes thinned down to a knife edge.
To prevent both grooving of the container side wall and excessive thinning of the flange type edge during the aforementioned spin flow necking process, a cam ring is secured to the slide roll to present a cam follower surface which is contacted by the form roll during radial inward advancing movement of the latter at the on-set of the necking-in process. The cam follower surface and the conical surface of the form roll facing the cam follower surface are further arranged to produce the following motions:
In FIG. 3A, the form roll axis has moved radially inwardly closer to the container axis and has started to form the neck. The conical surface 24e on the eccentric roll 24 has forced the form roll 11 toward the open end C" of the container C. The form roll 11 has just touched the cam follower surface 104. The small radius 106 on the form roll 11 is very close to the small radius 108 on the slide roll 19' but does not pinch the metal between these two points. This is because the cam ring follower surface 104 is positioned so these radii 106,108 may approach each other but stay separated by a distance slightly greater than the initial side wall thickness. This is presently understood to be a key feature in the elimination of metal exposure and neck cracks caused by excessive contact pressure between the two small radii 106,108 in the uncontrolled collision of the form roll 11 with the metal wrapped around the small radii 108 on the slide roll 19 in the prior spin flow necking process described hereinabove. In other words, since the form roll 11 contacts the cam follower surface 104 as the two radii 106,108 approach, such contact results in retraction or rearward axial sliding movement of the slide roll 19' which permits the two radii to move past each other.
In FIG. 3B, the form roll 11 has penetrated further between the eccentric roll 24 and the slide roll 19'. The small radius 106 on the form roll 11 is just passing the small radius 108 on the slide roll 19'. The rolls 11,19' do not pinch the metal but have moved closer. As mentioned above, the form roll 11 is forcing the slide roll 19' back by contact between the form roll and the cam ring 102 instead of contact at this point between the form roll and the slide roll as occurred in the aforesaid prior spin flow necking process.
In FIG. 3C, the form roll 11 has continued its penetration and the small radius 106 is past the small radius 108 on the slide roll 19' (point A). At this point, the conical surfaces 19a,11b on the slide roll and the form roll, respectively, are opposite and parallel each other. The slide roll 19' and cam ring 102' have been pushed to the left in FIG. 3C. The combination of the metal thickening as a result of being squeezed between the form roll 11 and the eccentric roll 24 as the metal wraps around the forming surface 11a of the form roll, and the shape of the left or trailing conical surface 11b on the form roll, has reduced the relative clearance between the form roll and the slide roll so that the form roll is now actually putting slight pressure on the metal.
In FIG. 3D, the form roll 11 has now penetrated further into the gap between the eccentric and slide rolls 24,19'. The form roll 11 is clearly clamping the metal between it and the slide roll 19' and, as a result, a gap 130 may open up between the form roll surface 11b and the cam ring follower surface 104. The form roll 11 is now pushing the slide roll 19' directly in the axially rearward direction through its contact with the metal, and not through the cam ring 102. Since the small radii 106,108 between the form roll 11 and slide roll 19' have already "slipped" past each other without undesirable grooving of the metal therebetween, the direct interaction of the form roll in thinning and shaping the metal against the bias of the conical surface 19a on the slide roll is important to ensure proper necking and distribution of metal.
In FIG. 3E, the form roll 11 has now penetrated to its radially inwardmost position to complete the formation of the spin flow neck. During the entire forming process, between 20 to 24 revolutions of the container C are required, depending on the diameter, thickness and the amount of diameter reduction in the container end. The rolling contact between the form roll 11 and the slide roll 19' has thinned the edge of the flange slightly. Therefore, in accordance with a further feature of this invention, the form roll 11 now once again contacts the cam ring 102 to prevent further thinning of the flange area of the container C, i.e., gap 130 has closed.
The foregoing cam ring improvement to the spin flow necking process is disclosed in U.S. patent application Ser. No. 07/929,933, filed Aug. 14, 1992, by Harry W Lee, Jr. et al, which application is assigned to Reynolds Metals Company, the assignee of the present application. The disclosure of this application is hereby incorporated by reference herein in its entirety.
The cam ring advantageously eliminates the grooving and cut necks, as well as excessive thinning of the flange, that were prevalent before its introduction. However, the interaction of the outer form roll with the eccentric and slide rolls to achieve the final necked-in state depicted in either FIG. 2E (no cam ring) or FIG. 3E (with cam ring) has been discovered, through extensive experimentation, to directly affect the plug diameter (i.e., the inner diameter of the necked-in portion such as measured at 124 in FIG. 2E) and the length of flange 123, with or without the cam ring, and at any given base pad setting (i.e., the fixed distance during necking between the base pad 29 supporting the can bottom and the axially immovable eccentric roll), resulting in unacceptable variations therein. In a can plant environment, particularly when employing numerous necking-in tooling assemblies in a multi-station machine of the type disclosed in U.S. patent application Ser. No. 07/929,932, filed Aug. 14, 1992, by Harry W. Lee, Jr. et al, entitled "Spin Flow Necking Apparatus and Method of Handling Cans Therein", now U.S. Pat. No. 5,282,375 granted Feb. 1, 1994, assigned to Reynolds Metals Company, the present assignee, control over the plug diameter and flange width achieved with the tooling assembly at each station is critical to achieving homogeneity in product and successful continuous operation. The disclosure of the '932 application is hereby incorporated by reference herein in its entirety.
It is accordingly an object of the present invention to prevent unacceptable variations in can plug diameter and flange length during the spin flow necking process.
Another object is to control the interaction of the outer form roll with the inner slide roll to ensure such uniformity in plug diameters and acceptable plug diameter variation.
Yet another object is to control the aforesaid interaction between the outer form roll and the inner slide roll with the can by limiting the final movement of the inner slide roll and thereby the final movement of the outer form roll so that the final radially inward advancing movement of the latter is directly controlled by controlling the movement of the inner slide roll.
Yet another object is to provide a control mechanism that may be installed in each tooling assembly in the plant tool room so as to pre-set the movement of the inner slide roll to achieve the aforesaid uniformity in plug diameter, prior to installing the assemblies in a multi-station machine for continuous production of product.
Yet another object is to provide a plug diameter control mechanism which is simple in design, easy to install, and capable of rugged continuous operation without wear.
Disclosure of the Invention
An apparatus for necking-in an open end of a container body comprises a first member and a second member mounted for engaging the open end of the container side wall along an inner surface thereof. Means is provided for rotating the container body and externally located means moves radially inward into deforming contact with an outside surface of the container side wall in a region thereof overlying an interface between the first and second members. Such contact between the externally located means with the side wall causes the contacted wall portion to move radially inwardly into a gap formed at the interface, caused by axial separation of the first and second members under the action of the radially inward advancing movement of the externally located means into the gap to thereby neck-in the side wall. In accordance with the present invention, means is provided for limiting the final axial movement of the first member which in turn controls the final radially inwardmost location of the externally located means to ensure substantially uniform plug diameters in the necked-in cans.
In the preferred embodiment, the radial movement of the externally located means is cam controlled and the means for limiting its final radially inwardmost location overrides the radial movement otherwise provided through the camming surface.
In the preferred embodiment, the first member is a slide roll engaging and supporting the inside of the container open end. The slide roll is mounted for driven rotary motion about, and axial movement along, the container axis. The slide roll is resiliently biased into the container open end. The second member is an axially fixed roll mounted in axially inwardly spaced relation to the slide roll for engagement with an inside surface of the container side wall. The second roll has a conical end surface which faces the open end of the container and the slide roll includes a conical end surface facing the conical end surface of the axially fixed roll in opposite inclination thereto. The externally located means is a form roll having a peripheral deforming nose positioned externally of the container side wall and mounted for free rotary and controlled radial movement towards and away from the container. The form roll is biased for axial movement along an axis parallel to the container axis. The form roll deforming nose includes first and second oppositely inclined conical surfaces which are respectively opposed to the conical surfaces on the second roll and slide roll.
The limiting means preferably includes a stop spacer means which is fixedly mounted to a tooling spindle housing supporting the first and second rolls. The spacer means includes a stop surface in axial alignment with a rearward facing movable annular surface of the slide roll assembly. Without the spacer means, the slide roll assembly is normally free to move (against resilient bias) in the axially rearward direction towards the spindle housing as a result of camming engagement with the cam controlled, radially and axially movable outer form roll, without "bottoming out" of the slide roll assembly against the spindle housing. However, with the spacer means of the present invention, the stop surface contacts the slide roll assembly to prevent further axial retracting movement thereof before the cam controlled outer form roll has otherwise completed its radially inward movement as a result of cam follower action. Stopping of the slide roll assembly in this unique manner prevents further radially inward advancing movement of the outer form roll which advantageously results in substantially uniform plug diameters in successively necked cans.
The spacer means of the present invention is preferably used in combination with the cam ring improvement mounted to the slide roll radially outwardly adjacent therefrom.
A method of spin flow necking-in an open end of the cylindrical container body is also disclosed. The method comprises the steps of positioning inside the container body an axially fixed roll engageable with the inside surface of the container body. The axially fixed roll has a sloped end surface which faces the open end of the container body. A slide roll is also positioned inside the container body which fits the inside diameter of the open end to support same. The slide roll has an end which faces the sloped end surface of the axially fixed roll. The slide roll is supported for axially displacement away from the axially fixed roll. The slide roll end and the sloped end surface of the axially fixed roll define a gap therebetween. An outer form roll is positioned opposite the gap radially outwardly from the container body for axial displacement away from the axially fixed roll during contact with the sloped end of same. The form roll has a trailing end portion and a peripheral forming portion. As the container body spins, the form roll is advanced radially inwardly relative to the gap so that the trailing end portion presented by the roll and the sloped end surface of the axially fixed roll engage the container body between them while a trailing end portion of the form roll moves inwardly along the sloped end surface of the axially fixed roll to roll a neck into the container body. As the body continues to spin while the form roll moves inwardly, the slide roll is retracted axially until the roller has spun an outwardly extending portion on the end portion of the container body engaged between the slide roll and the container. In accordance with the method of the invention, the final axial retracting movement of the slide roll is controlled by having the slide roll contact a spacer fixedly mounted axially rearwardly of the slide roll. Such limiting contact prevents further radially inward advancing movement of the outer form roll by overriding the cam follower movement of the outer form roll. This in turn produces substantially uniform plug diameters in the necked-in containers.
In accordance with a further feature of the invention, the axial retracting movement of the slide roll, prior to contacting the spacer, is controlled by contact between a surface of the form roll with a cam follower surface. More specifically, the form roll has conical surfaces which are respectively engageable with the sloped end surface of the axially fixed roll and another sloped end surface on the slide roll. These form roll conical surfaces are smoothly connected with a curved forming surface extending therebetween and defined by a pair of small radii. The sloped end of the slide roll is also smoothly connected through another small radius to the axially extending surface thereof which is engageable with the inside surface of the container body. The cam follower surface operates to axially retract the slide roll as the small radius on the form roll approaches the small radius on the slide roll to thereby prevent pinching of the container side wall between these two small radii by allowing the radii to approach each other while maintaining separation therebetween by a distance slightly greater than the original thickness of the container side wall. Continued radially inward forming movement past a predetermined point at which the metal of the container side wall between the slide roll and the conical surface of the form roll has thickened will result in the form roll putting slight pressure directly on the metal. A gap opens between the form roll and cam follower surface so that the form roll is now pushing the slide roll directly through contact with the metal and not through contact with the cam follower surface. As the outermost end of the container side wall moves between the form roll and the slide roll, the form roll will once again contact the cam follower surface so that the rolling contact between the form roll and the slide roll does not excessively thin the edge of the open end. As this occurs, the slide roll will contact the spacer means and thereby be prevented from further axial retracting movement. The conical interconnection through the cam follower surface thereby prevents further radially inward movement of the form roll.
Still other objects and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description, wherein only the preferred embodiments of the invention are shown and described, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawing and description are to be regarded as illustrative in nature, and not as restrictive.